Bain marie is double boiler, put a heat proof bowl over a pot of simmering water. Put the chocolate and cream in the bowl, do not let water vapor get in the bowl with the chocolate. Stir to melt the chocolate. Continue recipe!

If you're British, it's a double boiler. If you're not, it's a hot water bath. That's the literal translation. For this recipe, yes a stainless steel bowl over gently simmering water (NOT BOILING) to melt the chocolate is what you're looking for